1. Field of the Invention
The present invention relates to a deinterlacing method based on a motion-compensated interpolation (MCI).
In particular, the present invention relates to a method for converting video signals of an interlaced scanning format into those of a progressive scanning format, that is, a deinterlacing method for video signals.
More particularly, the present invention relates to a deinterlacing method for video signals in which an MCI is taken into consideration in a conversion of video signals of an interlaced scanning format into those of a progressive scanning format.
Furthermore, the present invention relates to a deinterlacing method for video signals in which involves estimating a motion vector for a current block by the unit of a xc2xd pixel and the unit of a xc2xc pixel, deinterlacing the current block, based on the estimated motion vector, conducting a side-effect check for the MCI-based deinterlacing, and outputting the result of the MCI-based deinterlacing or outputting the result of a deinterlacing conducted based on a method other then the MCI, in accordance with the result of the side-effect check.
2. Description of the Prior Art
In present television systems, a specific scan format so called an xe2x80x9cinterlaced scan formatxe2x80x9d is adopted. In accordance with an interlaced scanning format for NTSC television systems, odd and even lines of 525 scan lines are outputted to a display in an alternating fashion at intervals of a {fraction (1/60)} second for every picture. On the other hand, odd and even lines of 625 scan lines are outputted to a display in an alternating fashion at intervals of a {fraction (1/60)} second for every picture in accordance with an interlaced scan format for PAL systems.
Here, respective pictures outputted at intervals of a {fraction (1/60)} second are referred to as xe2x80x9cfieldsxe2x80x9d. A complete picture consisting of two fields is referred to as a xe2x80x9cframexe2x80x9d.
A field consisting of odd scan lines is referred to as an xe2x80x9codd fieldxe2x80x9d or a xe2x80x9ctop fieldxe2x80x9d whereas a field consisting of even scan lines is referred to as an xe2x80x9ceven fieldxe2x80x9d or a xe2x80x9cbottom fieldxe2x80x9d.
The interlaced scan format, in which every frame is outputted to a display in a state divided into two fields, provides an advantage in that it can reduce the bandwidth of TV signals by xc2xd, as compared to a non-interlaced progressive scan format in which all scan lines of every frame are outputted in a {fraction (1/60)} second.
If TVs of the present NTSC television system, which uses a bandwidth of 6 MHz by virtue of the above mentioned interlaced scan format adopted thereby, did not adopt the interlaced scan format, they would require a bandwidth of about 12 MHz.
In spite of an advantage in that the bandwidth required for signal processing can be reduced, the interlaced scan format involves a drawback in that when a video having horizontal fine line patterns is displayed on a display, those fine line patterns may be chattered at a frame frequency of 30 Hz. That is, a large-area flickering phenomenon may occur.
Where the video displayed on the display contains an object flickering at 30 Hz, there is a problem in that fine line patterns may be viewed in an overlapped state over the object.
The above mentioned phenomena, which result in a degradation in picture quality, are inevitably involved in the interlaced scan format.
However, the advent of digital TV systems has caused picture quality to be considered as a very important factor.
Advanced Television Systems Committee (ATSC) standard for digital TV signals adopts both the progressive scan format and the interlaced scan format.
For instance, TV standard for a size of 704 pels*480 lines adopts a 60 Hz progressive scan format and a 60 Hz interlaced scan format.
In the case of a digital TV receiver adopting a progressive scan format, video signals of such an interlaced scan format should be converted into those of a progressive scan format.
On the other hand, where TV signals are to be displayed on the monitor of a PC via a TV receiver card mounted to the PC, it is necessary to convert TV signals of an interlaced scan format into those of a progressive scan format because the monitor can display only videos of the progressive scan format.
Thus, the conversion of video signals from the interlaced scan format into the progressive scan format is essentially required in various cases.
Mainly, there are two methods for the conversion of video signals from the interlaced scan format into the progressive scan format.
The first method is an inter-field interpolation, and the second method is an intra-field interpolation.
A simple example of the inter-field interpolation is a weave method in which one frame is formed by combining one top field and one bottom field.
In accordance with this method, however, horizontal lines disturbing to the eye are formed at a moving portion of the displayed video even though a good display result is obtained in associated with the still portion of the video. This is because there is a timing difference between the two fields.
A more complex example of the inter-field interpolation is a motion-compensated interpolation.
In accordance with the motion-compensated interpolation, motion information is extracted from a frame in order to conduct a desired line interpolation. Based on the extracted motion information, empty lines of the current field are interpolated by the previous field or the further previous field.
In this case, it is important to allow the motion compensation to be accurately carried out.
Meanwhile, a simple example of the intra-field interpolation is a bob method in which one frame is formed using the scanning lines of one field two times.
In accordance with this method, it is possible to prevent horizontal lines disturbing to the eye from being formed at a moving portion of the displayed video. However, there is a complexity in forming frames. Furthermore, the fine portions of the displayed video may be chattered at 30 Hz.
Furthermore, a degradation in vertical resolution is involved in this method. In particular, a distortion in a stepped shape is generated at edge portions of the displayed video.
A more complex example of the intra-field interpolation is an edge-directional interpolation (EDI).
In accordance with this EDI, only the pixels of the current field are used to interpolate the empty lines of the current field. In particular, the directions of edges are detected in order to carry out the interpolation based on the information detected.
Therefore, it is important to detect the edge directions accurately.
Generally, one of the above mentioned methods, either MCI or EDI, is selectively used for conventional deinterlacing techniques.
Most commercially available TV receiver cards allowing TV signals to be displayed on a PC monitor are configured to select a desired one of bob and weave modes using a control program.
Even in the case in which a complicated algorithm is implemented using a VLSI chip, a fundamental type of the EDI is implemented in most cases.
For the MCI, there are few examples in which a deinterlacing chip is used.
However, present VLSI techniques have reached a level capable of implementing a considerably complex MCI algorithm.
In this regard, the present invention proposes a high performance MCI algorithm which can be implemented using a VLSI chip.
Therefore, an object of the invention is to provide a deinterlacing method for video signals based on an MCI, in which an MCI algorithm can be implemented, in a deinterlacing for video signals of an interlaced scan format into a progressive scan format, by use of a VLSI chip capable of obtaining video signals of a progressive scan format, while minimizing a degradation in picture quality.
In accordance with the present invention, this object is accomplished by providing a deinterlacing method for video signals based on a motion-compensated interpolation comprising the steps of: (a) estimating a motion vector by the unit of a xc2xd pixel and the unit of a xc2xc pixel, respectively, using a previous frame, a current field, and a future field; (b) interpolating empty pixels of the current field by pixels of the previous frame designated by the estimated motion vector, thereby deinterlacing the current field; (c) conducting a side-effect check for determining whether or not the result of the deinterlacing is satisfactory; and (d) if the result of the side-effect check is satisfactory, then outputting the result of the deinterlacing as a deinterlaced value of the current field, and if not, then outputting the result of a deinterlacing conducted in accordance with a method other than that of the step (b).